During the first year of the grant the emphasis was put on the analysis of receptors in the brain of various strains. This work will continue during the second year with expansion of the study of additional strains. The main emphasis in the second year will be on measuring the distribution of peptidases in the brain in various strains. Our assay methods have worked out and tested, and we will be able to analyze for several enzymes and test some of their properties. Cerebral amino peptidase, carboxypeptidases, and carboxydipeptidases activity will be measured with several substrates. The continuing aim of the study is to examine genetic differences in a. receptors, b. their neurotransmitter ligands, and c. the enzymes controlling the metabolism of these neurotransmitters. We hope to correct changes in distribution of these parameters with behavioral changes and changes of pharmacological responses.